I've also noticed that cheap bags for hunters use duck, not goose down. However, the lightest of all, and the most expensive, is down from the Eider duck, so they say. You have to hand-pick the stuff from unused nests, since it is an endangered species (I read somewhere). So, at least some ducks are cooperating with the UL movement.

From :http://www.featherind.com/FAQ.html#66. WHICH BIRDS PROVIDE THE BEST DOWN?
Generally speaking, the best down comes from larger, more mature birds. When age and maturity are equal, goose down is better than duck down. However, down from an older duck is better than down from a younger goose. Larger Down has an extraordinarily high warmth-to-weight ratio. A duvet or sleeping bag filled with this down will be very light and incredibly warm. And it will last for decades.

On the other hand, poor quality White Goose Down will have smaller Down. It will not loft up, and has a rather low warmth-to-weight ratio. Even if there is more of this down by weight, it won't be as warm. Down from younger birds not only tends to have poor filling power, it will also tend to collapse in a relatively short time, because its fibers are too fragile. This is usually the difference between an inexpensive goose down product, and an expensive one7. WHAT IS EIDERDOWN?
Eiderdown comes from the Eider Duck, and it is considered by some to be the finest quality of all down. It is also the most expensive. This down is unique in that it clings to itself, resulting in superior insulating power. The Eider Duck is a protected migratory species. Down is collected by hand from nests without disturbing the birds

Can 90 (white duck) is a odorless down because it is processed properly.
The fill power is very high because it is from an older mature duck which has larger and denser down clusters. It is also 90% down content by weight.
It is cheaper than lower filling power goose down, because it is duck. There is much more duck down produced in the world than goose down. More ducks are raised for their meat than geese. It is also a marketing advantage that retailers and merchandisers have promoted for many years, "goose down is the best". But that is simply not true. You must compare "apples to apples".